1. Field of the Invention
The present invention relates to an improved organophilic clay gellant and processes for preparing organophilic clay gellants. The organophilic clay gellants of the present invention may be used to thicken a variety of organic compositions such as polyester compositions.
2. Description of the Prior Art
The preparation of organophilic clay gellants is well documented in the art. The gellants have been prepared from a variety of compounds, such as certain amines, but has more typically been prepared from "onium" compounds, most notably ammonium, phosphonium and sulfonium, with ammonium compounds being the most widely used. Exemplary descriptions of long known techniques for preparing organophilic clay gellants are set forth in U.S. Pat. Nos. 2,531,427, 2,859,234 and 2,966,506.
In the evolution of organophilic clay gellants, certain organic cations or organic cations and organic anions have been developed which impart improved characteristics to the organophilic clay gellants. For example, the ease of dispersion and/or efficiency of the organophilic clay gellants may be significantly improved by using certain organic cations or combinations of organic cations with organic anions. Illustrative patents which describe such improved organophilic clay gellants are U.S. Pat. Nos. 4,105,578, 4,208,218, 4,287,086, 4,391,637, 4,410,364, 4,412,018, 4,434,075, 4,434,076, 4,450,095 and 4,517,112.
The basic process for preparing the organophilic clay has remained fairly standard. In particular, the clay is treated so as to place inorganic cations, such as potassium. magnesium and most preferably, sodium, on the exchange sites. There is some indication in the art, such as in British Patent 1,106,281, that the presence of the sodium ions is important to achieve swelling of the clay. An aqueous slurry of the clay is then heated and reacted with an organic cation which is originally associated with an anion which can be an acetate (see U.S. Pat. No. 2,704,276) or hydroxyl (see U.S. Pat. No. 2,879,229) or possibly some organic anion (see U.S. Pat. No. 4,317,737), but is typically chloride as can be seen from the U.S. Patents mentioned above. If an organic anion is also used to prepare the organophilic clay gellant, it is typically prepared in the form of an acid or salt.
The reaction product (i.e., the organophilic clay gellant) of the cation exchanged clay and the organic cation and, if present, the organic anion is separated from the slurry, washed and dried and the residual liquid is discarded.
While certain improvements in the organophilic clay gellant have been obtained by subjecting a slurry of the clay to high shear conditions prior to reaction with the organic cation, using dilute reaction conditions when the clay is reacted with the organic cation and, if present, the organic anion and employing gentle drying of the organophilic clay gellant, as disclosed in commonly assigned U.S. Pat. application Ser. No. 767,599, filed on Aug. 20, 1985, now U.S. Pat. No. 4,695,402, it is desirabale to achieve further improvements in organophilic clay gellants and the processes for preparing them.